Block copolymers of various structures have been known for some time. Commonly, two or more blocks are combined in a single polymer which possesses different physical and/or chemical character to make a material having properties that are some combination of those individual blocks. In this way, mono-alkenyl arenes and conjugated dienes have been employed as monomers for such blocks prepared by anionic polymerization. The glassy blocks comprising mono-alkenyl arenes provide physical strength and the rubbery blocks comprising conjugated dienes provide elastomeric character. When arranged in the proper structure such block copolymers, often generically referred to as styrenic block copolymers, form thermoplastic elastomers.
U.S. Pat. No. 3,670,054 to De La Mare et al. discloses block copolymers that have a reduced sensitivity to organic solvents. In particular the block copolymers disclosed include selectively hydrogenated (polybutadiene-polystyrene-polyisoprene-polystyrene-polybutadiene). In addition to possessing the glassy character of polystyrene and the rubbery character of polyisoprene, these block copolymers also possessed some character typical of semi-crystalline polymers since the hydrogenated polybutadiene blocks resembled polyethylene.
U.S. Pat. No. 4,107,236 to Naylor et al. discloses a hydrogenated block copolymer having the structure hydrogenated low vinyl butadiene block-polystyrene block-hydrogenated medium vinyl butadiene block-polystyrene block-hydrogenated low vinyl butadiene block (lvB-S-mvB-S-lvB). Upon hydrogenation, the low vinyl butadiene blocks become semi-crystalline polyethylene and the medium vinyl butadiene block becomes ethylene/butylene rubber.
U.S. Publ. No. 2010/0056721 to Wright et al. discloses selectively hydrogenated linear or radial styrenic block copolymers having terminal semi-crystalline blocks resulting from the hydrogenation of low vinyl butadiene blocks. The block copolymers were used neat or in melt-processed compounds for a variety of film, fiber and molding applications.
U.S. Pat. No. 5,737,469 discloses a gel composition comprising a mineral oil and hydrogenated styrenic block copolymer that makes a gel for the optical fiber cable industry. Optional components are a thixotropic agent and an antioxidant. Once the gel is formed it has high viscosity even in its initial state. As such, these gels are difficult to pump into the small voids and interstices present in cable constructions.
U.S. Pat. No. 6,881,776 discloses two-phase gel compositions obtained by mixing a gelled ester composition comprising a mixture of: 1) an ester compound and a polymer compound selected from the group consisting of triblock copolymers, star polymers, radial polymers, multi-block copolymers, and a combination thereof, and 2) a hydrophobic, non-polar solvent. The disclosed technology comprises use of two separate solvents/solutions to make a composition which had relatively low viscosity upon initial formation but became a cohesive gel upon heating. Such compositions are relatively complex since two different components are separately prepared and then combined.
There continues to be a need for simple formulations which have initially low viscosity and which are very pumpable and yet can be converted to a gel when the non-flowable gel state is desired. In this way cables could be formed with which it would be possible to convert an initially grease-like substance to a non-flowable gel. This would be advantageous for the repair or splicing of the cables. The repair or splicing site would be more solid in character and the cable filling would not flow from the repair or splicing site.